A. Field of the Invention
This invention relates to a method for preventing caking of a body of granulated sodium chloride particles containing, or in an environment conducive to the formation of, sodium sulfate and/or sodium carbonate impurities, while the body of particles is maintained within the temperature range of from about 610.degree. C. to at least about 700.degree. C. One particular aspect of this method provides an improvement in incineration processes utilizing a fluidized bed of sodium chloride by permitting higher, more efficient operating temperatures.
B. Description of the Prior Art
It is known in the art to dispose of organic waste contained in aqueous effluent streams also containing inorganic solids, by incineration in or over a bed of fluidized granular material. See, for example, Copeland et al, U.S. Pat. No. 3,309,262; Albertson et al, U.S. Pat. No. 3,319,586; and Mallat et al, "Incinerate Sludge and Caustic," Hydrocarbon Processing, pp. 121-122, May, 1970.
To briefly summarize such incineration processes, a bed of particles is maintained in a dense turbulent suspension in an upflowing stream of a hot, oxygen containing gas. Typically, the hot oxygen containing gas is at least partially comprised of gases from the combustion of a sulfur containing fuel in air, and therefore contains carbon dioxide, sulfur dioxide, and water vapor in addition to oxygen. The waste stream to be disposed of is customarily sprayed into the bed itself or into the so-called freeboard above the bed. Upon contact with the bed the organic components are oxidized to water, carbon dioxide, and the like, and are vented to the atmosphere along with water vapor from the aqueous portion of the waste stream. The solid inorganic material remaining becomes part of the bed itself. Portions of the bed are removed as the process continues, to compensate for the addition of the solid inorganics from the waste stream. Although an inert material, such as sand, may be used for the bed during start-up, it is apparent that at least after a period of operation, the bed will have a composition substantially corresponding to the inorganic portion of the waste stream.
While the teachings of the prior art appear to be generally applicable to a wide variety of waste streams, a particular problem has heretofore been encountered when attempts were made to incinerate a sodium chloride based stream containing organic matter. A typical effluent stream from a methylcellulose plant for example, is a sodium chloride brine stream containing such organics as glycols and glycol ethers as well as traces of methylcellulose. Although partial oxidation of the organic compounds occurs at somewhat lower temperatures, it is most efficient to incinerate such a waste stream at temperatures within the range of from about 650.degree. C. to about 680.degree. C. Prior to the invention hereinafter described and claimed, however, sodium chloride bed temperatures much in excess of about 600.degree. C. could not be sustained. At temperatures slightly above 600.degree. C., caking, i.e., agglomeration or conglomeration of the bed particles, began to occur.